KEYCLOAK-14019 Improvements for request_uri configuration

upgrading/topics/keycloak/changes.adoc

@@ -1,5 +1,15 @@
 == Migration Changes
 
+=== Migrating to 12.0.2
+
+==== Valid Request URIs
+
+If you use the OpenID Connect parameter `request_uri`, a requirement exists that your client needs to have `Valid Request URIs` configured.
+This can be configured through the admin console on the client details page or through the admin REST API or client registration API. Valid Request URIs need
+to contain the list of Request URI values, which are permitted for the particular client. This is to avoid SSRF attacks. There is possibility to use wildcards
+or relative paths similarly such as the `Valid Redirect URIs` option, however for security purposes, we typically recommend to use as specific value
+as possible.
+
 === Migrating to 12.0.0
 
 ==== Upgrade to Wildfly 21